RD-1: Added an inital port of d_main.c/d_main.h. Added some other basic files

src/math/m_fixed.rs

@@ -0,0 +1,47 @@
+/* Implemnetation of *m_fixed.c/h
+
+This provides fixed-point arithmetic as 32-bit 16.16
+*/
+
+pub const FRACBITS: i32 = 16;
+pub const FRACUNIT: i32 = 1 << FRACBITS;
+
+pub const MININT: i32 = 0x80000000;
+pub const MAXINT: i32 = 0x7fffffff;
+/// Struct representing a fixed point 32-bit value
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub struct FixedPoint {
+    pub value: i32,
+}
+
+impl FixedPoint {
+
+    #[allow(non_snake_case)]
+    pub fn FixedMul(a: FixedPoint, b: FixedPoint) -> FixedPoint {
+        let value = ((a.value as u64) * (b.value as u64) >> FRACBITS) as i32;
+        FixedPoint{value}
+    }
+
+    #[allow(non_snake_case)]
+    pub fn FixedDiv(a: FixedPoint, b: FixedPoint) -> FixedPoint {
+        if (i32::abs(a.value) >> 14) >= i32::abs(b.value) {
+            if a.value^b.value == 0 {
+                FixedPoint{value: MININT};
+            }
+            else {
+               FixedPoint{value: MAXINT};
+            }
+        }
+        FixedPoint::FixedDiv2(a,b)
+    }
+
+    #[allow(non_snake_case)]
+    pub fn FixedDiv2(a: FixedPoint, b: FixedPoint) -> FixedPoint {
+        let c: f64 = ((a.value as f64) / (b.value as f64)) * FRACUNIT as f64;
+        if c >= 2147483648.0 || c < -2147483648.0 {
+            panic!("FixedDiv: divide by zero");
+        }
+        FixedPoint { value: c as i32 }
+    }
+
+}